Tri Epsilon Delta is a location in or near 24th century Federation space, somewhere in the galaxy's Alpha or Beta Quadrants.
History and specifics[]
In the 2360s decade, Tri Epsilon Delta was near Tholian borders. In the year 2367, there was a Tholian raid on this location, and Commodore Terman brought the hospital ship USS Curie to provide assistance. This was his most recent assignment prior to the rescue mission to the planet Penzatti. (TNG novel: Vendetta)